A mixture of 2-Amino-1-propyl-8-[1-(3-trifluoromethyl-benzyl)-1H-pyrazol-4-yl]-1,7-dihydro-purin-6-one (prepared as given in Example 13) (0.169 g, 0.41 mmol), isoamyl nitrite (0.2 ml, 1.5 mmol), iodine (83 mg, 0.32 mmol) was taken in THF (5 ml) and stirred for 2 hours at 80° C. Reaction mixture was cooled and saturated solution of Na2S2O3 was added and extracted with ethyl acetate (3×5 ml). The organic layer was washed with brine (10 ml), dried over Na2SO4 and evaporated to obtain 2-Iodo-1-propyl-8-[1-(3-trifluoromethyl-benzyl)-1H-pyrazol-4-yl]-1,7-dihydro-purin-6-one (93 mg, 44%).
